Method and apparatus fob



w 8, 1 2 n R Aug. 19, 194i.

M. F RISCH METHOD AND APPARATUS FOR COMBUSTION original Filed Jan. 21,1935 5 Sheets-Sheet l INVENTOR. /VA/W//v FQ/SCH @ff/7M ATTORNEY.

Aug. 19, 1941. M. FRlscH METHQD AND APPARATUS FOR COMBUSTION4 OriginalFiled Jan. 2l, 1955 5 Sheets-Sheet 2 lill:

INVENTOR. Mfwr//v FTQ/5CH @V4-5dr" ATTORNEY` M. FRISCH METHOD ANDAPPARATUS FOR COMBUSTION Aug. 19, 1941.

Original Filed Jan. 2l, 1935 INVENTOR.

ATTORNEY.

Aug. 19, 1941. M-FmscH Re. 21,878V

METHOD AND APPARATUS FOR GOMBTJSTION Original Filed Jan. 21, 1955 5Sheets-Sheet 4 ATTORNEY.

Aug. 19, '1941. mm1-SCH l Ra 21,878

METHOD AND' APPARATUS FOR COMBUSTION oginal Filed Jan. 21, 1955 v5sheets-sheet 5 INVENTOR. /V/ffr//v 51750/ ATTORNEY.

i BY l Reuued Aug. A19, 1941 ulSuTl-ED'l STATES PATENT OFFICE Ma'r'nonAND APPARATUS ron. coMnUs'rroN Martin Frisch, New York, N. Y., assixnorto Foster Wheeler Corporation, New York, N. Y., a corporation of NewYork Original No. 2,118,600, dated May 24, 1938, Serial No. 2,622,January 21, 1935. Application for reissue February 10, 1940, Serial No.318,378

19 Claims.

This invention relates to the combustion of fuels and provides novelmethods and apparatus for producing the combustion of fuels entrained incurrents or streams of air.

'I'he invention is capable of effective application the burning of awide variety of fuels but is particularly useful for the combustion ofprulverized fuels of low volatility. With low volatile fuels, such ascertain anthracite and bituminous coals, it is desirable that the ratioof fuel to the carrying air which is delivered to the furnace by theburners be high so that ignition may be easily produced and maintainedand it is also desi; ...ble that the velocity of the air fuel mixturedelivered by the burners be low for, the reason that the velocity offlame propagation of such mixtures is ordinarily very low.

The methods and apparatus of the present in- Fig. 10 is a sectional viewon an enlarged scale drawings.

vention readily and efficiently effect the control Y of the richness ofa fuel and air mixture which is delivered to fuel burners from thesource of"`sup ply to provide the degree of richness of the mixturewhich is delivered by the burners to the furnace for eilicientcombustion. 'I'he invention also provides an effective control of thevelocity at which the combustible mixture of desired richness isdelivered by the burners to the furnace. Other features and advantagesof the invention will be perceived from the following descriptionconsidered in connection with the accompanying drawings, forming a partthereof, in which the embodiments of the invention which have beenselected for disclosure are illustrated.

In the drawings:

Fig. l is a view in elevation with parts in section, of apparatus forproducing combustion which embodies the present invention;

Fig. 2 is a front elevational view of the apparatus shown in Fig. 1;

Fig. 3 is a sectional elevational view on an enlarged scale of theburner shown in Fig. 1;

Fig. 4 is a transverse sectional view taken on line 4-4 of Fig. 3;

Fig. 5 is a sectional view taken on line 5-5 of Fig. 6;

Fig. 6 is a sectional view taken on line B--G of Fig. 5;

Fig. 7 is a sectional view taken on line 1-1 of Fig. 3;

Fig. 8 is a sectional View taken on line 8--8 of Fig. 1;

Fig. 9 is a view in elevation with parts in section, of another form ofapparatus embodying the invention;

The forms of the invention disclosed are arranged for producingcombustion in the furnace of steam generating apparatus but it will beunderstood that the invention is not limited to this producingcombustion in any other furnace.

Referring particularly to Figs. 1 to 8 inclusive,

reference character 20 designates the furnace of a steam generatorhaving a setting 2l and a steam and water drum 22. The steam generatormay be of any desired form. The system disclosed in these figures of thedrawings effects the reduction of the fuel to finely divided form. theentraining of the reduced fuel Ain a current of air and the delivery ofthe fuel and air mix,- ture directly to the furnace by means of burnersembodying the invention. The fuel, anthracite or bituminous coal in thisinstance, is delivered to the feed pipes 23 and is conducted through thefuel feed portion of a classifier 24 into the pulverizing mill 25 of anysuitable type. The mill comprises a rotatable drum having pulverizingmeans-such as a plurality of steel balls of varying diameters. Air,preferably preheated, is introduced into the mill through the air inletI9 and sweeps entirely through the mill over the surface of the fuelbeing pulverized therein and picks up the reduced fuel and carries itthrough the classifier 2l wherein the fuel particles which have not beensufliciently pulverized are separated from the fuel and air stream andare returned to the mill 25. The air stream and entrained pulverizedfuel then flows through discharge pipe 2B into an exhauster 21 which isdriven by suitable means such as the electric motor I8. A damper I1 ishingedly mounted in pipe 26 and is movable between a position in whichpipe 26 is fully open and an opening il is completely closed and aposition in which pipe l fuel and air mixture to burners 38 which embody*the invention.

The burners 36 are arranged to discharge vertically downwardly throughburner ports 3| in a horizontally disposed wall 32 of the boiler setting2|. Suitable means indicated 33 are pro- `\vided for supporting theburners 38 in proper position relative to the ports 3|. Referringparticularly to Figs. 3 to 6 inclusive, each burner 38 comprises a pairof contiguous cylindrical casings 34 having open lower ends with acentrifugal separator 35 disposed in its upper portion, a nozzle 88 inits lower portion and a tubular member 31 which is gradually contractedtoward its lower end and which connects the separator and the nozzle.The upper ends of members 31 are welded or otherwise secured to theinterior of the casings 34 and the lower ends 38 are threaded forconnection to the upper ends of the nozzles 88. The lower ends of thecylindrical casings 34 fit into cylindrical apertures in a member 39which engages the setting 2| and the walls of ports 3|, and the upperends of the casings are the degree to which the fuel and air mixturedelivered to the separators is enriched and also to control the velocityat which the enriched fuel and air mixture is delivered by the nozzlesto the furnace. In this instance. such means consists of verticallyreciprocable valves 66 which may be closed and held togethervby a cover48. 'I'he fuel v rection to the separators 35 through adjacentlydisposed inlet ports 42 in the walls of casings 34. The stream of fueland air delivered to the burners is divided by the vertically disposededges 43 of the casings 34 at the contiguous sides of ports 42, into twoapproximately equal portions, each of which is caused to flow in aspiral path toward the nozzles 36 in the annular space 46 between thecasing 34 and the tubular outlet 48 which extends downwardly from thecover 48 and is coaxially disposed in the upper part of the casing 34. Aportion of the stream of fuel and air owing through each separator 35 iscontinually withdrawn through the outlet 48 and is delivered through theconnection 58 to a delivery pipe 5| which may conduct the separated airand any fuel entrained therein to any point desired. In this instance,the separated air and fuel is delivered to the furnace as part of thesecondary air supply as will hereinafter be described. The Withdrawal ofpart of the air from the main air stream ilowing through the spaces 46,concentrates the fuel in the remaining air thereby enriching the fueland air mixture which enters the members 31. The enriched mixture flowsdownwardly through the members 31 and is delivered to the nozzles 36. Asshown, the lower ends of the nozzles 36 are bent or curved so that thefuel is delivered to the furnace in a downwardly, vertically inclineddirection. Operating rods 64 which project through and move in slots inthe casings 84, provide means for rotating the nozzles 36 about theiraxes with respect to members 31 so that the fuel and air jets deliveredby the nozzles may be directed as desired to impinge upon each other ornot as desired. Means are provided for throttling the upper ends of thenozzles 38 in order to provide for the control 0f described asconsisting of two frusta-conical sections with a common base. Thesevalves are mounted adjacent the lower ends of l valve rods 58 which.extend upwardly through the members 31- and separator outlets. 48 andare supported in tubular supports 88 on member 58. The upper end of eachof the valve rods 58 is provided with an operating handle 62 and thatportion of each valve rod which lies in the zoneof and adjacent to thesupport 68 is provided with ay series of small apertures 84 throughwhich a pin 66 may be inserted to retain the valve and the rod in thedesired adjusted position. The lower end of each valve rod 58 isprovided with a suitable guiding member 88 which engages the innercylindrical surface of lthe upper end of nozzle 36 to maintain thecoaxial vrelationship between the nozzle and the valve. As shown. themaximum diameter of the valves 56 is smaller than the inside diameter ofthe upper ends of the nozzles 36 so that the nozzles are nevercompletely closed by these valves. The cylindrical casings 34 are eachprovided with openings in their central portions in the zones of themembers 31, through which secondary" air may be introduced into thefurnace at the burner nozzles through the space 61 between the easing 34and the members 31 and nozzles 36. These openings are closed by hingeddoors 68 provided with means for cla'mping them in adjusted positionwhich comprises a lever 69 fixed at one end to the door and having athreaded member 18 secured to its other end which moves in an arcuateslot in a plate 18 secured to casing 34. A nut 18' on the end of anoperating handle provides the 'clamping action required. Each burner isprovided with an ignition opening in member 39 adjacent the nozzles 36,which is closed by a hinged cover 1|.

'Ihe lean mixture or the portion of the air and the fuel entrainedtherein which is separated from the main or orginal mixture in eachburner, is delivered b y the pipes 5| through ports 12 in the wall 13 ofthe setting 2|. The discharge end 14 of each pipe 5| is provided with avalve 15 which may be a check valve or may be controlled by suitablemeans depending upon the circumstances of operation. An air casing 16spaced from the walls of the setting 2|, provides a passageway 11through which airis delivered to the furnace 28 through a plurality ofsecondary air ports 18. These ports 18 are controlled by valves 18 whichare supported on and are operated by valve rods 80. Each of these rods88 has an arm 8| nxed to its outer end which is pivotally connected toan operating rod 82. Rod 82 is vertically or axially reciprocated by ahand wheel 83 threaded to the upper end of the rod. An indicator 84 onthe upper end of rod 82 provides means by which the extent to which theports 18 are opened maybe visually determined.

The operation is as follows: Almixture of primary air and pulverizedfuel entrained therein is withdrawn from mill 25' and after passingthrough the classifier 24 is withdrawn through pipe 28 by the exhauster21 and is delivered to the distributor 28 which more or ls uniformlydistributes the mixture to the several pipes 26 through which themixture is delivered to the separators 35 of the burners 36. In owingdownwardly in a spiral path through the annular spaces Il of theseparators 85,'the greater por- -ftion of the pulverized fuel is throwntoward the outer peripheral portions of the streams or toward thecasings 8l and upon reaching thelower ends of the outlets 48, portionsof the moving air streams together with relatively small portions of thefiner particles of the entrained fuel are withdrawn through the outlets48 and flow v separators 35 into the nozzles 36 and is dischargedthereby into the furnace where it is burned. The velocity at which theenriched primary air and fuel mixture is discharged into the furnace isdetermined by the positions of valves 56, or in other words, isdetermined by the extent to which the inlet ends of the nozzles 96 areopened or closed by these valves. These valves also control the extentto which the mixture of primary air and fuel is enriched since theycontrol the difference in pressure between the nozzle inlets and theseparator outlets 48. Secondary air in the volumes necessary forcombustion may be introduced through the secondary air inlet ports inthe burners which are controlled by doors 68 and through the ports 18 inthe side Walls of the furnace.

With this arrangement it will be perceived that fuels of low volatilitymay be satisfactorily and eiciently burned for the reason that thevelocity at which the primary air and fuel mixture is delivered to thefurnace by the burners may be readily and accurately controlled and theratio of fuel to air in the air fuel mixture delivered to the furnace bythe burners may also be readily and accurately controlled. Economy inoperation is effected by this arrangement since the air and fuel mixturewhich is separated from the main fuel and air stream, is delivered tothe furnace to support combustion. The range of the control effected bythis arrangement may be illustrated from the following: The rich mixtureor concentrate delivered to the furnace by the burners may contain froml5 to 35% of the original primary air which is delivered to the burnermixed with from to 90% of the fuel delivered to the burner. The leanmixture separated from the main stream of primary air and fuel and whichis delivered to some point in the furnace outside of the ignition zoneof the enriched mixture or to any other desired point, will contain fromto 65% of the air in the original stream which is delivered to theburners and from 10 to 35% of the fuel originally delivered to theburners.

Another arrangement embodying the invention is illustrated in Figs. 9and 10. In this arrangement, a different form of separator is employedwhich is disposed at some distance from the burners. The separatorindicated 85 has an inlet 86 connected to the discharge end of a pipe 29which conducts the primary air and fuel mixture from the distributor 28.The inlet 86 of the separator is connected to inlets 81 and 88 ofsimilar but oppositely arranged separator casings 89 and 90,respectively, both of which are arranged to provide spiral paths yofflow 9| of the fuel and air r mixture therethrough. Centrifugal forceacting upon the fuel particles entrained in the air streams causes themto be more or less concentrated in the outer peripheral portions of thestreams thereby enriching these portions which pass through a pluralityof spaced baille plates 92 and thence through outlets 93 and 94,respectively, into and through pipes 95 to the burners 96 which may be,of any suitable form or design. Portions of the air streams flowingthrough the spiral flow paths 9| are withdrawn through outlets 91 ancl`98 respectively, and are delivered through pipes 99 to the furnace 20adjacent the burners 96 or to any other point in the furnace, or to anypoint outside ofl or remote from, the furnace 20. At the point at whichthe fuel and air mixture is delivered to the inlets 81 and 88 by pipe8.6, switching valve |00` is provided so that the burner 96 connectedwith either of the pipes 95 may be shut down Without disturbing theoperation of the other. Valve |00 is double faced and self ,seating andis movable about a pivot |0| by any suitable operating means into andout of engagement with seats |02 and |09 in inlets 81 and 88respectively. A shield |04 in inlet 86 protects the valve from theabrasive action of the fuel when both inlets 81 and 88 are fully open,at which time the valve |00 is positioned in vertical alignment with theshield |04. Valves |20 similar to the valve 15, are provided for thepipes 99. Valves |20 may be of the check type or may be controlled bysuitable means to control the extent to which the fuel and air mixturewhich is delivered to the burners, is enriched.

A further arrangement embodying the invention is shown in" Figs. 1l to15 inclusive. In this arrangement the fuel and air mixture is deliveredthrough pipes 29 to elbows 4I through which it delivered to twoadjacently disposed burners |05 and |06. Each of these burners comprisesan upper cylindrical portion I 01, an intermediate portion |08 ofgradually restricted flow area downwardly, a lower cylindrical portion|09 having a distributing cone |I0 closing its lower end and nozzles I II and I2 connected at their upper ends to the portion |09, atdiametrically opposed points as may be seen from Fig. 14 particularly.The nozzles have a rectangular flow area in this instance and nozzle ||2isY directed vertically downwardly while nozzle I is directed in avertically inclined direction toward the nozzle IIZ. The arrangement issuch that the fuel and air jets discharged from ythe nozzles do notimpinge upon each other. The lower portions of the outer side Walls |I3and |I4 of the nozzles III and I|2 respectively, are removable and arehinged at their upper ends I|5 and. I I6 respectively to the nozzles toprovide regulating valves for the nozzles to control the velocity atwhich the enriched fuel and air mixture is discharged into the furnaceand also to provide a control for the degree to which the originalmixture delivered to the burners is enriched. The upper portion |01 ofthe burners acts as a separator and the separated portions of the airand entrained fuel are withdrawn through outlets II1 and are deliveredthrough a pipe II8 to the pipes 5|. In view of the foregoing descriptionof the operation of the burners disclosed in Figs. 1 to 8, the operationof this form of burner will be apparent.

pulverized form is delivered from the source of supplyto the burnersentrained inair ofsumcient quantity to carry the fuel to the burners.Prior to the injection of the fuel into the furnace for combustion, theoriginal fuel and air mixture is enriched to the extent desired for themost eilicient'burning of the fuel and the velocity at which theenriched mixture is delivered to the furnace is controlled to providethe most eilicient burning from the standpoint vof llame propagation.

Although a so-'called unit system has been dis-- closed withoutdeparting from the invention, it-

will be understood that I do not intend to limit the invention except bythe scope of the appended claims.

What is claimed is:

l. Apparatus for producing combustion of fuel in a furnace comprising aseparator, means for supplying the fuel entrained in a stream of air tothe separator, -means for withdrawing part of the air from said mixtureto thereby enrich the remaining mixture, a plurality of nozzles throughwhich the enriched mixture is delivered to the furnace for combustion inan ignition section thereof, a valve for controlling the flow area ofeach nozzle to control the degree to which said mixture is enriched, andmeans for delivering the air withdrawn from said mixture. to the furnaceoutside said ignition section andat an elevation spaced substantiallyfrom the elevation at which the enriched mixture is delivered to thefurnace to support combustion of said enriched mixture. v

2. Apparatus for producing combustion of fuel in a furnace comprising aseparator, means for supplying the fuel entrained in a stream of air tothe separator, means for withdrawing part of the air from said mixtureto thereby enrich Ithe remaining mixture, a plurality of nozzles throughwhich the enriched mixture is delivered to the furnace for combustion inan ignition section thereof, one of the walls of each of said nozzlesbeing movable to control the degree to which said mixture is enriched,and means for delivering the 'air withdrawn from said mixture to thefurnace outside said ignition section to support combustion of saidnriched mixture.

3. Apparatus for producing combustion of fuel in a furnace comprising aseparator, means Yfor' supplying the fuel entrained in a stream of airto the separator, means for withdrawing part of the air from saidmixture to thereby enrich the remaining mixture, aburner nomle throughwhich the enriched mixture is delivered to the furnace for combustion inan ignition section thereof, one of the walls of said nozzle beingmovable to control the flow area of said nozzle to control the degree towhich said remaining mixture is enriched, and means for delivering theair withdrawn from said mixture to the furnace outside said ignitionsection to support combustion of said enriched mixture.

4. 'I'he method of producing combustion of fuels which comprisesentraining the fuel in a stream of air, causing said fuel and air streamto flow in a curved path, withdrawing part of the air from Cil zone torejoin the burning enriched mixture.

5; 'I'he method of producing combustion of fuels which comprisesentraining the fuel in a stream of air, causing said fuel and air streamto flow in a curved path, withdrawing part of the air from the fuel andair stream as it flows through the curved path to enrich the remainingmixture,

delivering the enriched mixture in a vertically A downward directionthrough a wall of the furnace for combustion in an ignition zone,controlling the nozzle to thereby control the degree to which saidremaining mixture is enriched, and delivering the separated air to thelfurnace outside of and below said ignition zone and through another wallof the furnace to rejoin the burning enriched mixture.

6. Apparatus for producing combustion of fuel in a furnace comprising aburner, means for supplying fuel suspended in a stream of air to theburner, means for withdrawing part ofthe air from said stream to therebyenrich the remaining fuel and air mixture, means for delivering theenriched mixture to the furnace for combustion through one wall of thefurnace, and means for delivering the air withdrawn from the stream tothe furnace outside of and below the ignition section of the` furnacethrough another wall thereof to rejoin the burning enriched mixture.

'7. Apparatus for producing combustion of fuel in a furnace comprising aplurality of separators.

a single conduit for delivering fuel entrained in astream of air to eachof said separators, means for withdrawing part of the air from thefuelair mixture in each separator to thereby enrich the remainingmixture, a nozzle for each separator through which the enriched mixtureis delivered to the furnace for combustion in an ignition sectionthereof, and means for delivering the air withdrawn from said mixture ineach separator to the furnace outside, of and below said ignitionsection and at an elevation spaced substantially from the elevation atwhich the' enriched mixture is delivered to the furnace to Iejoin saidburning enriched mixture.

8. Apparatus for producing combustion of fuel in a furnace comprising aplurality of separators,

a single conduit for delivering fuel entrained in a stream of airto'each of said separators, means for withdrawing part of the air fromthe fuel-air mixture in each separator to thereby enrich the remainingmixture,a nozzle for each separator through which the enriched mixtureis delivered to the furnace for combustion in an ignition sectionthereof, each nozzle having a discharge end disposed at an angle to theaxis of the nozzle, means for moving each nozzle about its axis to varythe direction in which the enriched mixture is discharged from thenozzle, and means for delivering the air withdrawn from said mixture ineach separator to the furnace outside said ignition section to rejoinsaid burning enriched mixture.

9. Apparatus for producing combustion of fuel in a furnace comprising aplurality of separators, means for delivering fuel entrained in a streamof air to each of said separators, means for withdrawing part of theairfrom the fuel-air mixture nueve said mixture in each separator to thefurnace i outside said ignition section to support combustion of saidenriched mixture.

10. The method of producing combustion of fuels which comprisesentraining the fuel in a stream of air. separating part of the` air fromsaid stream thereby enriching the remaining fuel and air mixture,delivering the enriched mixture to the upper portion of a furnace forcombustion in an ignition zone and delivering the separated air to alower portion of the furnaceoutside said ignition zone to rejoin theburning enriched mixture. 11. The method of supplying pulverized fuel toa furnace for combustion which comprises entraining the fuel in a streamof air, delivering the fuel and air mixture to a separating zone.

, separating part of the air from said stream thereby enriching theremaining mixture. delivering 'the enriched mixture to the upper portionof the furnace through one wall thereof for combustion in an ignitionzone and delivering the separated air to the furnace through anotherwall thereof outside of said ignition zone and at a lower portion of thefurnace to rejoin the burning enriched mixture.

12. The method of producingcombuston of fuels which comprises entrainingthe fuel in a stream of air, causing said fuel and air stream to flowinto a separating zone, separating. part ofthe air from said streamthereby enriching the remaining fuel and air mixture, delivering theenriched mixture in a vertically downward direction to the upper portionof a furnace for combustion in an ignition zone, and delivering theseparated air to a lower portion of the furnace outslde'said ignitionzone to rejoin the burning enriched mixture.

13. Apparatus for producing combustion of fuel in a furnace comprising aseparator, means for supplying the fuel entrained in a stream of air tothe separator, means for withdrawing part of the air from said mixtureto thereby enrich the remaining mixture, a burner nozzle disposed todeliver the enriched mixture to the upper portion of the furnace forcombustion in an ignition section thereof, and conduit means having itsdischarge located to deliver the air withdrawn from said mixture to thefurnace outside said ignition section in a lower portion of the furnaceto rejoin said burning enriched mixture.

14. Apparatus for producing combustion of fuel in a, furnace comprisinga separator, means for supplying the fuel entrained in a stream of airto the separator, means for withdrawing part of the air from saidmixture to thereby enrich the remaining mixture, a burner nozzledisposed to deliver the enriched mixture to the furnace in the upperportion thereof for combustion in an ignition section of the furnace, avalve for controlling the nozzle thereby to control the degree to whichthe mixture is enriched, and conduit means having its discharge locatedto deliver the air withdrawn from said mixture tothe furnaceY outsidesaid ignition section and in a-lower portion of the furnace to rejoinsaid burning enriched mixture. i

15. Apparatus for producing combustion of fuel in a furnacecomprlsing aplurality of separators, a single conduit for delivering fuel entrainedin a stream of air to each of said separators, means for withdrawingpl'tlof the air from the fuelair mixture in each separator to therebyenrich the remaining mixture, means connected to each separator andlocated to deliver the enriched mixture to the upper portion of thefurnace for combustionin anignition section thereof, valve means forcontrolling the delivery of fuel entrained in air to the separators, andconduit` means for delivering the air withdrawn from said mixture ineach separator to a. lower portion of the furnace and outside saidignition sec-'- tion to rejoin said burning enriched mixture.

16. Apparatus for producing combustion of fuel in a furnace comprising aplurality of separators adjacently disposed and located in a wallbounding an upper portion of the furnace, a single conduit fordelivering fuel entrained in a stream of air to each of said separators,means for withdrawing part of the air from the fuel-air mixture in eachseparator to thereby nrich the remaining mixture, a nozzle for eachseparator through which the enriched mixture is delivered to the upperportion of the furnace for combustion in an ignition section thereof,and conduit means having its discharge located to deliver the airwithdrawn from said mixture in each separator to the furnace outsidesaid ignition section at an elevation lower than and spaced from saidnozzles to rejoin said burning enriched mixture.

17. Apparatus for producing combustion of fuel in a furnace comprising aplurality of separators adjacently disposed and located in a wallbounding an upper portion of the furnace," a single conduit fordelivering fuel entrained in a stream of air to each of said separators,means for withdrawing part of the air from the fuel-air mixture in eachseparator to thereby enrich the remaining mixture, a nozzle for eachseparator disposed to deliver the enriched mixture to the furnace at theupper portion thereof for combustion in anv ignition section, andconduit means for delivering the air withdrawn from said mixture in eachseparator to the furnace outside said ignition section through a sideWall of th'e furnace at an elevation lower than and spaced fromsaidrnozzles to rejoin said burning enriched mixture.

18. The method of producing combustion of fuels which comprisesentraining the fuel in a stream of air, owing the fuel and air mixturethrough a path sufficiently curved to effect a con- 'centratlon of amajor portion of the fuel into a. minor portion of the air to provide anenriched fuel and air mixture, withdrawing the enriched mixture anddelivering it in a downwardly direction to one portion of the furnacethrough one wall thereof for combustion in an ignition zone, anddeliveringl the remaining portion of the original fuel and air mixtureto another part of the furnace through another wall thereof at a pointremote from the point at which the enriched mixture is delivered to thefurnace so that said remaining portion flows in the furnace free of saidignition zone but into contact with the burning enriched mixture.

19. Apparatus for producing combustion of fuel in a furnace comprising aseparator having an inlet for a fuel and air mixture, a passagesufi'iciently. curved to eifect a concentration of a major portion ofthe fuel in said mixture into a minor portion of the air thereof toprovide an 5 enriched fuel and air mixture, the separator having anoutlet for the enriched mixture and another outlet for the remainingmixture. a burner nomic connected to said outlet and disposed to deliverthe enriched mixture in a downwardly 10 direction to one portion of thefurnace through one wall thereof for combustion in an ignition sectionthereof, and conduit means connected to said other outlet and having itsdischarge l0- cated in another wail thereof and directed to deliver theremaining mixture to the furnace at a point remote from said burnernozzle and so that the remaining mixture nows in the furnace free ofsaid ignition zone but into contact with the burning enriched mixture.

MARTIN FRISCH.

